1. Technical Field
This application generally relates to data storage, and more particularly to techniques used in connection with data migration.
2. Description of Related Art
Computer systems may include different resources used by one or more host processors. Resources and host processors in a computer system may be interconnected by one or more communication connections. These resources may include, for example, data storage devices such as those included in the data storage systems manufactured by EMC Corporation. These data storage systems may be coupled to one or more host processors and provide storage services to each host processor. Multiple data storage systems from one or more different vendors may be connected and may provide common data storage for one or more host processors in a computer system.
A host processor may perform a variety of data processing tasks and operations using the data storage system. For example, a host processor may perform basic system I/O operations in connection with data requests, such as data read and write operations.
Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units, disk drives, and disk interface units. Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass. and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., U.S. Pat. No. 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels to the storage device and storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical disk units, logical devices or logical volumes. The logical disk units may or may not correspond to the actual physical disk drives. Allowing multiple host systems to access the single storage device unit allows the host systems to share data stored therein.
At various times, there may be a desire or need to migrate data from one location to another, such as migration of user data from a source logical volume to a target logical volume, or to swap a first logical volume with that of a second logical volume (e.g., so that data of the first logical volume is stored in the storage area of the second logical volume, and vice versa).
One technique that may be utilized includes making the source volume unavailable for use such as to an application, copying the data to the target volume, and then making the data on the target volume available for use by the application. The foregoing may be undesirable or unacceptable due to application usage requirements and expectations as well as regulatory requirements. For example, the foregoing may require stopping and then restarting the application to use the data from the new target logical volume. It may be desirable to have such data migration occur with minimal disruption and as transparently as possible with respect to applications and other software using and processing such data.